package com.jiesone.logger.distributecleaning.util;

import org.springframework.stereotype.Component;
/**
 * 分布式雪花ID算法
 *
 * @author zhi
 * @since 2019年5月14日16:51:06
 *
 */
@Component

public class SnowFlake {


        /**
         * 起始的时间戳
         */
        private final static long twepoch = 1557825652094L;

        /**
         * 每一部分占用的位数
         */
        private final static long workerIdBits = 5L;
        private final static long datacenterIdBits = 5L;
        private final static long sequenceBits = 12L;

        /**
         * 每一部分的最大值
         */
        private final static long maxWorkerId = -1L ^ (-1L << workerIdBits);
        private final static long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
        private final static long maxSequence = -1L ^ (-1L << sequenceBits);

        /**
         * 每一部分向左的位移
         */
        private final static long workerIdShift = sequenceBits;
        private final static long datacenterIdShift = sequenceBits + workerIdBits;
        private final static long timestampShift = sequenceBits + workerIdBits + datacenterIdBits;

        private long datacenterId; // 数据中心ID
        private long workerId; // 机器ID
        private long sequence = 0L; // 序列号
        private long lastTimestamp = -1L; // 上一次时间戳

        public SnowFlake(long workerId, long datacenterId) {
            if (workerId > maxWorkerId || workerId < 0) {
                throw new IllegalArgumentException(
                        String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
            }
            if (datacenterId > maxDatacenterId || datacenterId < 0) {
                throw new IllegalArgumentException(
                        String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
            }
            this.workerId = workerId;
            this.datacenterId = datacenterId;
        }

        public  SnowFlake(){
            new SnowFlake(0,0);
        }

        public synchronized long nextId() {
            long timestamp = timeGen();
            if (timestamp < lastTimestamp) {
                throw new RuntimeException(String.format(
                        "Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
            }
            if (timestamp == lastTimestamp) {
                sequence = (sequence + 1) & maxSequence;
                if (sequence == 0L) {
                    timestamp = tilNextMillis();
                }
            } else {
                sequence = 0L;
            }
            lastTimestamp = timestamp;

            return (timestamp - twepoch) << timestampShift // 时间戳部分
                    | datacenterId << datacenterIdShift // 数据中心部分
                    | workerId << workerIdShift // 机器标识部分
                    | sequence; // 序列号部分
        }

        private long tilNextMillis() {
            long timestamp = timeGen();
            while (timestamp <= lastTimestamp) {
                timestamp = timeGen();
            }
            return timestamp;
        }

        private long timeGen() {
            return System.currentTimeMillis();
        }

}
